Global temperatures in 2023 soared to unexpected heights, sparking concern among climate scientists. With an increase of nearly 0.3°C over the previous year, the dramatic rise initially puzzled experts. James Hansen, a renowned climate scientist, suggested this could mark the beginning of a new phase in global warming, accelerated by the reduction in air pollution. NASA's Goddard Institute for Space Studies Director, Gavin Schmidt, suggested this unusual rise might reveal gaps in our understanding of climate feedback mechanisms.
El Niño as a Key Contributor
However, recent studies indicate the tropical Pacific Ocean's shifting conditions, including the transition from a La Niña to a strong El Niño, may hold the key to explaining these anomalies. El Niño has long been known for its capacity to disrupt global climate patterns. During a La Niña event, trade winds push warm water towards Indonesia, allowing cooler deep water to surface in the eastern Pacific, lowering global temperatures.
In contrast, El Niño brings warmer waters back eastward, effectively switching off the ocean's “air conditioner.” Studies led by Shiv Priyam Raghuraman at the University of Illinois Urbana-Champaign suggest that the end of a prolonged La Niña, combined with the onset of a robust El Niño, is responsible for 2023's temperature spike.
A Rare but Possible Phenomenon
The team analysed 58,021 years of climate model simulations to understand how often such spikes occur. They found that large temperature increases following El Niño are rare, occurring only 1.6 percent of the time. However, when preceded by a long La Niña, the probability of such a spike rises to 10.3 percent.
Their findings align with another study, co-authored by Marianne Tronstad Lund from Norway's Centre for International Climate and Environmental Research, which highlighted that the global oceans, though warmer in 2023, weren't significantly hotter than during past El Niño events.
A Climate Debate that Continues
While El Niño is seen as the primary driver of 2023's record heat, scientists like Schmidt remain cautious. The speed and duration of the warming event surpassed typical El Niño patterns, with lingering heat as Earth heads towards another La Niña.
Additionally, the increase in sunlight detected by satellites, potentially due to reduced cloud cover or surface reflectivity, raises further questions. For now, El Niño appears to be the most likely culprit, but the broader climate debate continues.
